1. Field of the Invention
This invention relates to a seat, and more particularly to a seat for use in an automotive vehicle.
2. Description of the Prior Art
There is an increasing demand for improving the function and design of a seat, especially, a bucket seat for use in an automotive vehicle, while, at the same time, a greatest possible reduction of the manufacturing cost of such a seat is also demanded. Thus, there is antinomy between these contradictory demands. The present invention is intended to deal with these antinomic demands. Examples of prior art seats to be improved by the present invention will first be described before describing the seat of the present invention, so that improvements made by the present invention can be clearly understood.
FIGS. 5a to 5j show examples of prior art seats. FIG. 5a or 5b is a schematic sectional view taken along the line Va--Va in FIG. 5c which is a plan view of a prior art seat. FIG. 5a shows that a trim cover 4 is bonded at its entire back surface to a molded polyurethane foam 1. This trim cover 4 is formed by previously lamination-bonding a filler pad 3 to a cover member 2. Black dots in FIG. 5c and short hatchings in FIGS. 5a and 5b indicate the spots or portions 5 where the trim cover 4 is bonded to the molded polyurethane foam 1. FIG. 5b shows that the trim cover 4 is composed of the cover member 2 only.
Such a prior art seat is made by the steps of placing the trim cover 4 at a predetermined position in a molding cavity of a foaming mold and foaming a polyurethane resin solution in the mold to form the molded polyurethane foam 1 integrally combined with the trim cover 4. Generally, impregnation or permeation of the polyurethane resin solution into the trim cover 4 during foaming is utilized to attain the desired bonding. However, when the trim cover 4 is thin as in the case of FIG. 5b bonding utilizing the permeation of the polyurethane resin solution is not preferable.
When the seat is made according to such an integrally foaming and molding method, various defects as schematically shown in FIG. 5d occur frequently. A first defect is the occurrence of a fold 6a. FIG. 5e is an enlarged sectional view taken along the line c-d in FIG. 5d to show such a fold 6a. When a slack remains on a flap part of the cover member 2 at the time of manufacturing the seat, and the polyurethane resin solution is foamed to integrally combine the molded polyurethane foam 1 with the cover member 2 in such a state, the cover member 2 and the molded polyurethane foam 1 are bonded together while the fold 6a is formed on the cover member 2.
A second defect is the presence of a peeling portion or a floating portion as indicated at 6b in FIG. 5d. As best shown in FIG. 5f which is an enlarged sectional view taken along the line g-h in FIG. 5d, such a peeling or floating portion 6b occurs as a result of local insufficient bonding.
A third defect is the presence of a cave-in as shown at 6c in FIG. 5d. As best shown in FIG. 5g which is an enlarged sectional view taken along the line e-f in FIG. 5d, a portion of the molded polyurethane foam 1 directly beneath the cover member 2 is depressed during foaming and molding, resulting in formation of the cave-in 6c.
A fourth defect is the occurrence of a crease as shown at 6d in FIG. 5d. The detail of this crease 6d is shown in FIG. 5h which is an enlarged sectional view taken along the line i-j in FIG. 5d.
Because the trim cover 4 and the molded polyurethane foam 1 are firmly integrally bonded together, repair of these defects is impossible in most cases, resulting in the loss of the otherwise beautiful external appearance of the seat.
Further, when a side part A and a flap part B of the trim cover 4 are sewn together along a seam 10 as shown in FIG. 5i, part of the polyurethane resin solution tends to exude to the outside through this seam 10, resulting in exposure of a portion 1a of the molded polyurethane foam 1. Such external exposure is undesirable in that the beautiful external appearance of the seat is greatly impaired.
Further, a decorative groove or grooves 7 may be formed on a seat base part C of the seat from the design requirement, as shown in FIG. 5d. For the formation of such a groove 7, a foaming mold 8 having a corresponding convex portion 8a (FIG. 5j) is used during foaming and molding the polyurethane resin solution to make the molded polyurethane foam 1. However, that portion of the trim cover 4 may not be sufficiently shaped to conform to the shape of the convex portion 8a of the foaming mold 8, and the groove 7 may not have a sharply defined configuration. This is because the foaming pressure alone developed during foaming and molding the polyurethane resin solution to make the molded polyurethane foam 1 is not high enough to sharpen the contour of the corners of the groove 7, and a gap 9 tends to remain in that area.
Also, formation of a button-like pattern (as shown in FIG. 3c) may be required from the aspect of design. However, wrinkles around the buttons cannot be successfully produced when the trim cover 4 and the molded polyurethane foam 1 are entirely integrally bonded together.